Glucose is suggested to play a key role in motility hyperactivation of mammalian spermatozoa. The current study aimed to investigate the modulatory effects of silymarin and/or a protein kinase A (PKA) inhibitor (H-89) on glucose-mediated motility parameters of mouse spermatozoa. Spermatozoa were incubated in HEPES medium containing normal (NG; 5.5 mM) or high (HG; 25 mM) glucose concentration. The results of computer-assisted analysis showed that samples incubated in HG resulted in a larger (p<0.05) percentage of motile spermatozoa at 120 min (59.5 ± 14.8% vs. 34.0 ± 4.4%) compared to those incubated in NG. The average pathway velocity (VAP), curvilinear velocity (VCL), and straight-line velocity (VSL) exhibited similar patterns at 60 and 120 min when incubated in HG (p<0.05). Treatments with silymarin (5, 10, 20 μg/mL) did not significantly affect sperm motility under NG conditions, but decreased the HG-enhanced motility, VAP, and VCL at 120. min (p<0.05). H-89 (30 μM) reduced (p<0.05) motility at 30 min examined in the NG or HG medium. At 90 min, H-89 also reduced (p<0.05) the HG-enhanced motility of spermatozoa incubated with or without 20 μg/mL silymarin by 49% or 32%, respectively. In conclusion, the H-89-inhibition of glucose-mediated mouse sperm motility and certain types of velocity suggests that the glycolysis-PKA pathway is involved in the regulation of sperm motility. Silymarin may maintain sperm motility under NG conditions, but it inhibits glucose-activated sperm motility.
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